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Digital vs. Analog Radio-over-Fiber Fronthaul Architectures: a Total Cost of Ownership Assessment in 5G Scenarios
KTH, School of Information and Communication Technology (ICT).
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Future 5th generation of mobile wireless networks will have to support a data traffi c demand 100 times higher than current requirements. This increase will be supported by new improvements in the radio interface such as massive massive Multiple Input Multiple Output (mMIMO) and ultra-dense deployment of micro cells. In current Centralized Radio Access Networks (CRANs), BaseBand Units (BBUs) are co-located in a Central Offi ce (CO) and connected to Remote Radio Heads (RRHs) at the Base Station (BS) sites with an optical link connecting them, i.e., the Fronthaul. With current Radio over Fiber (RoF) technologies, the fronthaul required capacity may reach hundreds of Gigabits or even Terabits, according to the mMIMO configuration and

the type of beamforming used to direct the wireless signals towards the User Equipment (UE). This bandwidth “explosion” would require a huge number of transceivers and fibers in the transport network. This translates into a high cost for purchasing and installing the required equipment (i.e., CApital EXpenditures (CAPEX)) and to keep the network up and running (i.e., OPerational EXpenditures (OPEX)).

To decrease the required capacity in the fronthaul link it is possible to move back some of the baseband processing function to the BS site. Another approach consists in relocating the Digital to Analog Converter (DAC) function in the CO and sending analog signals over the optic link. This technique has been widely studied in Long Term Evolution (LTE) scenarios as effi cient and cost effective but shows weaknesses due to reach limitations and distortions caused by non-linear impairments when modulating the optical carrier with radio signals. Thus, an alternative fronthaul solution in 5th generation mobile networks is possible, but the trade-off between its reach, capacity, and cost needs to be better assessed.

This thesis evaluates three different RoF architectures (i.e., Analog Radio over Fiber (A-RoF), Digital Radio over Fiber (D-RoF) and Digital Signal Processing based Analog Radio over Fiber (DSP-ARoF)) to understand which one is the most cost effective solution for fronthaul links in 5th generation mobile networks. The study addresses a period of ten years and considers a dense urban scenario with Dense Wavelength Division Multiplexing (DWDM) as the transport technology. The work focuses on the Total Cost of Ownership (TCO) experienced by Mobile Network Operators (MNOs) when deploying a new infrastructure (i.e., trenching for the optical fibers), or reusing an existent one, (i.e., leasing dark fibers). Results show that Analog RoF is the most costly architecture because of the expensive analog components needed even if it minimizes the number of required fibers in optical links. Digital RoF requires a much higher number of fibers but equipment cost is lower due to the fact that the market is more mature. Finally, DSP-ARoF seems to be the most convenient solution because it has the same benefits of A-RoF concerning optical equipment and necessitates a smaller volume of expensive equipment. However, the analog approach does not provide a long reach thus D-RoF may remain the preferred solution in the presence of fronthaul links longer than 15-20 kilometers.

Place, publisher, year, edition, pages
2017. , p. 97
Series
TRITA-ICT-EX ; 2017:194
National Category
Computer and Information Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-227861OAI: oai:DiVA.org:kth-227861DiVA, id: diva2:1205414
Subject / course
Computer Science
Educational program
Degree of Master
Examiners
Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-05-14Bibliographically approved

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CiteExportLink to record
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